Implement universal Send To Rapp Command

Add a Send To R.app command so that anytime we need to send R commands we
can use this command instead of writing out the osascript implementation.
Also modified current commands to take advantage of the new system.

Added a settings file with the ability to set the app to send commands to,
also if they should be split into individual lines, or submitted as one
chunk, like the TextMate R bundle.
Change R build system to take advantage of Send to Rapp

Changed R build system to use the new R Source File command, which will
issue the source command only for .R files.
Add Set Working Directory command